I was raised by Godly parents, but these topics were never a part of our spiritual life (i.e we were allowed to swim mixed, public and private).
Since I made a personal choice to seek Jesus when I was 19 and have my own faith, and am pursuing Christ-likeness for myself, and my family, I am considering many social/cultural topics.
I am 42 and have an 8 year old daughter for whom these topics are future. I also have a toddler son for whom I will need to make whatever message consistent. 3 Points:
1. I remember being a teenager. As was pointed out in Mr. Parks response above, I was a male then, and am a male now, and while my responses to the visual temptations have changed, the temptations have not. I enter public pools with a dark tshirt, and long shorts only to play with my kids, and nephews, nieces. As I read and pray I have become increasingly convinced that exposing my body to anyone besides my wife does not honor God or Jesus. Currently I am against mixed bathing after awareness sets in (different age for every child – diligent parents will know). I have not had to address this with my daughter yet – so for now this is my conviction. For the record, I swam competitively for 8 years through my teen years in a racing suit, and spent entire days around females in racing suits. Sorry everyone, but awareness is awareness and it is no respecter of 1 pc or 2 pc suits (for males anyway).
2. Scripture teaches that the flesh affects the spirit and vice versa. While a saving relationship with Jesus is spiritual in origin, it must be carried out while flesh and spirit are still together. I’d be a hypocrit if I stated that I have always lived this way. As age and spiritual maturity increase choices change. The walk of faith in Jesus is a journey, not a destination. Time spent speaking to God in prayer, and listening to God in scripture will reveal answers to all our questions. Like any good relationship, it requires time. If heaven is your goal make this a priority.
3. At the risk of offending I’ll say that in observation of my own life, choices that are a result of what I want are by nature-selfish. 1 John 2:16 states that “the lust of the flesh, the lust of the eyes, and the pride of life is not of the Father, but of the world.” These 3 things produce self-satisfaction, and selfishness which do not in my life honor God. Jesus tells us to do unto as we would be done by. I’d prefer not to be tempted in this way, so will try not to tempt others in this way. Is this easy? No. Are followers of Jesus to be recognizeably different and unique from “the world”? Yes.

Final thought: It has been helpful to me to realize that God is present with me NOW. This both leads me to love myself and others more, and as a result helps me to honestly evaluate my motives for making choices.

Sorry this is so long.
Congratulations to the young lady for caring enough to seek answers at her age. I wish I’d been as thoughtful about faith and family when younger.

I recently read a manuscript by Stephen Higgenbotham on this subject that was excellent (I’ll try to send it to you). Refrencing Gen. 3: 7-11;21, when Adam and Eve were found naked in the garden and God gave them appropriate clothing, he pointed out that
1.) clothing was designed to cover our bodies, not show them off
2.) culture must not entirely determine what is modest or immodest because God gave them clothing to cover themselves better than leaves in a time when there was no culture.

So, I would ask, do even “modest swimsuits” cover your body or show off your curves? Even if everyone else is accustomed to swimming together, in swimsuits or bikinis, is that modest?

If you really want to swim with boys, and you are at a location where NO ONE ELSE is wearing swimsuits and bikinis, then why not wear dark, heavy material t-shirts and cut off jeans? You don’t have to wear a swim suit to swim. Some would even argue that a wet shirt is too clingy to wear in mixed company. How about a guy’s perspective?

The question I have for you is when does he give us that way of escape? Could it be in our decision to stay away from the temptation?
Now should one be involved in mixed swimming?
If what you wear doesn’t cause someone to have evil thoughts (at the pool, beach, mall, etc.) then it would be all right. What would be evil thoughts? Matt. 5: 28 Jesus said “But I say to you that whoever looks at woman to lust for her has already committed adultery with her in his heart.”
Now I want you to understand that this is not a one way street. It applies to both men and women.
I feel that anyone going to mixed swimming area is walking in an area that could be mighty dangerous.

Thank you from a mom who is struggling with a daughter who is more fascinated with the world than with Jesus.

God bless you all.